Powered hand hammer



April 9, 1968 R. K. WILLIS POWERED HAND HAMMER Filed May 10, 1966 f M MK D Q H m on United States Fatent O 3,376,940 POWERED HAND HAMMER Richard K. Willis, Rte. 28, Inlet, NY. 13360 Filed May 10, 1966, Ser. No. 549,004 Claims. or. 173-117 This invention relates generally to tools and more particularly to an electrically powered hammer.

Electrically powered hand hammers have been heretofore suggested for work in hard-to-get-at places but none have been successful because those in which a reciprocating head moves at right angles to the handle, the most effective type for reaching into awkward places, have never been completely self-contained. Those in which a motor is provided in the hammer itself have been too large and extend vertically from the working end too far to be effective when working in constricted places where an ordinary hand hammer cannot be swung.

The principal object of the present invention is to provide a hand hammer with a reciprocating plunger head moving in reverse directions normal to the handle, the plunger being driven by motor means contained in the handle.

Another important object is to provide means for reciproating the plunger in alternate work and return strokes in which the plunger is free to rebound independent of the remainder of the hammer after its work stroke. A further object is to provide a hammer having a generally conventional configuration with a reciprocating motor-driven plunger in the head, the motor being mounted within the handle and its speed being regulatable by a switch mounted on the handle.

Other objects and advantages will become apparent from the following description in conjunction with the accompanying drawing, in which:

FIGURE 1 is a side elevational View of a hammer according to the invention;

FIGURE 2 is a left end view thereof;

FIGURE 3 is a fragmentary sectional view on the line 3-3 of FIGURE 2;

FIGURE 4 is a sectional view on the line 44 of FIGURE 1;

FIGURE 5 is a fragmentary enlarged rear elevational View of the plunger as viewed from the right in FIGURE 1 and showing a portion of the drive pin engaged therewith;

FIGURES 6 and 7 are fragmentary enlarged side elevational and top plan views, respectively, of the parts shown in FIGURE 5;

FIGURE 8 is an enlarged front elevational view of I the plunger drive mechanism as viewed from the left in FIGURE 3; and

FIGURE 9 is a fragmentary side 'elevational view of a modified form of plunger on the same scale as FIG- URE 3.

In FIGURE 1 the hammer 10 comprises a head housing 11, provided with nail-pulling claws 12, and a handle 13 including a grip portion 14 secured to the housing 11 and an enlarged hollow free end portion 15 housing an electric motor 16 shown diagrammatically. A shut-off switch 17 for motor 16 is shown mounted on the grip portion 14 of the handle and a speed control switch 18 of the silicon rectifier type is shown mounted on the free end of handle 13. A flexible cord 19 extends from the free end of the handle for connecting motor 16 to a source of electric current and is connected in conventional manner through switches 18 and 17 to the motor. The source of electric current may be a conventional electric outlet or a battery pack carried by the operator.

The motor shaft 20 of motor 16 is elongated and extends the length of the handle, terminating within housing 11 and having a gear 21 fixed to its forward end. As best seen in FIGURE 3, gear 21 is housed in the rear portion 22 of housing 11 and is the first gear of a train of reduction gearing partially shown at 23-24 journalled in any convenient manner within housing portion 22. The driven or final gear 24 of the train is shown journalled on a stub shaft 25 fixed on a journal member 26 secured within the housing 11. Journal member 26 is shown as made of nylon plastic but may alternatively be of metal.

Housing 11 is made in two parts 11a and 11b secured together by the bolts or screws 27 which also secure journal member 26 within the housing. Portion 22 of the housing is shown as integral with the part 11b.

Forward of the gear 24 a plunger 30 is journalled for longitudinal reciprocating motion in the housing 11. The upper portion 30a is cylindrical and may slide up and down in a sleeve 31 secured to the top of housing 11. The lower portion of plunger 30 is widened as shown and has a fiat face slideable against the fiat forward face of the gear 24. Plunger 30 is also journalled for its reciprocating movement bythe portion 11a of the housing and by the journal member 26.

Around the sleeve 31, a coil spring 32 bearing on the shoulder between the upper and lower portions of the plunger, biases the plunger downward as viewed in FIG- URE 3.

The flat rear face of plunger 30 has a groove 33 thereacross, as best seen in FIGURE 5. Into the groove 33 a cog or drive pin 34 projects from the gear 24. The pin 34- may be shouldered, as shown in FIGURE 8, and secured in an appropriate hole 35 in gear 24 which is eccentric with respect to the center of rotation of the gear. Other holes such as that shown at 36 at a different radial distance from the center of rotation of the gear may be provided so that pin 34 may be removed from one hole and transferred to another.

Groove 33 is substantially of a width equal to the diameter of pin 34 about half way across the plunger. The groove is widened downward as shown for the remainder of the distance across the plunger.

Below the plunger 30, a separate reciprocating head or work member 37 is journalled coaxially with the plunger between the parts 11a and 11b of the housing. The head 37 is biased upward by the spring 38 bearing on collar 39 on the head so as to normally be in the path of the plunger 30, spring 38 being weaker than spring 32.

The head 37 is limited in its upward movement by a snap ring 40 seated in an appropriate groove around the portion of the head which protrudes from the end of housing 11. Another groove 41 may be provided for ring 40 to allow further upward movement of the head when pin 34 is placed in the hole 36 in gear 24.

In operation, hammer 10 is of conventional shape and may be used without training by anyone familiar with a conventional hand hammer. The hammer may be used in the conventional way without turning on the motor for starting a nail, for example. After the nail is started, motor 16 may be turned on by movement of the switch 17 and its speed regulated by turning the switch 18. Motor shaft 20 turns the drive or first gear 21 of the train of gears, the final gear 24 being driven at a considerably reduced rate.

The drive pin 34 is carried in a rotary path and on its down or work stroke is engaged in the narrow portion of groove 33. On the return stroke pin 34 engages the top of groove 33 for returning plunger 30 to its upper or withdrawn position. During the return stroke pin 34 is in the wider portion of groove 33 so that plunger 30 is free to rebound independent of the remainder of hammer 10 after it has completed its work stroke.

During the work stroke, when pin 34 is substantially half way in its downward movement, the lower end of plunger 30 meets the head member 37 and drives it downward compressing the spring 38. When head 37 is placed' on a nail, for example, the force of the blow of plunger 30 striking head 37 drives the nail into the wood in which it has been started, the plunger slowing in its downward movement as it approaches its lowermost position.

If the nail does not penetrate into the wood far enough to absorb the blow of the lowering plunger the hammer will recoil. Upon the completion of the work stroke of plunger 30, however, pin 34 reaches the wider portion of groove 33 and the plunger is free to recoil independently of the remainder of the hammer, pin 34 occupying a position in the lower portion of the groove as the plunger recoils upward. Thus rebound of the hammer is minimized and the head 37 tends to stay in contact with the nail head as the operator presses down on the hammer.

On the return stroke, pin 34 rises in the groove 33 until it reaches the top of the groove. As the pin continues to rise it thereafter carries plunger 30 upward compressing the spring 32 to add to the downward force of plunger 30 in its next work stroke.

Means are provided for changing the length of the stroke of plunger 30, for lighter work, for example. Screws 27 are removed and the two parts 11a and 11b of the housing are separated. This exposes the forward face of gear 24 and the drive pin 34 can be removed in any convenient manner from the hole 35 and placed in the alternate hole 36.

Snap ring 40 is then removed and placed in the alternate groove 41. Housing 11 is then reassembled and the parts secured by replacing screws 27. This adjustment requires partial disassembly but, unless the hammer is to be used for a considerable length of time for the lighter work, a somewhat similar effect can be obtained simply by slowing the motor by turning switch 18.

It will be apparent that the head 37 may be made integral with the plunger 30 so as to be carried with the plunger to the top of its return stroke and return spring 38 and snap ring 40 may be omitted. A modified form of plunger 30 is shown fragmentarily in FIGURE 9. Plunger 30 is the same as plunger 30 shown in FIGURES 2, 5, 6 and 7 except that plunger 30 has an integral work head 37 at its lower end similar in shape to head 37, the portion 37 being adapted to extend from lower end of housing 11 at least during the final portion of its work stroke.

As will be apparent to those familiar with the art, the invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The embodiments disclosed therefore are to be considered in all respects as illustrative, rather than restrictive, the scope of the invention being indicated by the appended claims.

What is claimed is: I

1. An electric power hammer comprising: an elongated head housing; a hollow handle extending laterally from the side of the housing, the handle having a forward end secured to the housing, an enlarged free end, and a reduced grip portion between the forward and free ends; an electric motor secured within the free end, the motor shaft extending through the grip portion into the housing; a motor shut-off switch mounted on the grip portion; a speed control switch for the motor mounted at the free end of the handle adjacent the motor; a reduction gear train having a plurality of gears including a first gear and 6 a final gear journalled within the housing, the first gear of the train being secured to the forward end of the motor shaft and the final gear having an eccentrically mounted drive pin projecting forward from its face; and a plunger journalled in the housing for receiprocating longitudinal movement therein adjacent the face of the final gear, the plunger having a slot thereacross adapted to receive the drive pin, whereby each rotation of the final gear drives the plunger in a work stroke in one direction and then returns the plunger in the opposite direction.

2. The power hammer as defined in claim 1 wherein the plunger is spring-biased in the direction of its work stroke and the width of the portion of the plunger slot containing the drive pin during the work stroke is substantially equal to the diameter of the drive pin and the remainder of the plunger slot has a width greater than the pin diameter whereby the plunger may rebound independent of the housing after the work stroke of the plunger.

3. The power hammer as defined in claim 2 wherein the plunger has a work portion extending outside the housing for at least a portion of its work stroke.

4. The power hammer as defined in claim 2 having a head member joumalled coaxially with the plunger in the housing for limited reciprocating longitudinal movement and normally projecting from one end of the housing, the head member being normally disposed in the path of the plunger in its work stroke and spring biased to a position in which it is struck by the plunger substantially midway in its work stroke.

5. A power hammer comprising: an elongated head housing; a plunger joumalled in the housing for longitudinal reciprocating movement therein and spring-biased in the direction from a withdrawn to an extended position; a tool head member journalled coaxially with the plunger for limited longitudinal reciprocating movement in the housing and having a portion normally projecting from one end of the housing, said member being spring biased toward a normal position so as to be struck by the plunger when it moves substantially half way from its withdrawn to its extended position and being movable against the bias of its spring when struck by the plunger; the plunger having a transverse fiat surface having a groove thereacross; a rotating element joumalled in the housing and having a face abutting the plunger fiat surface; a drive pin eccentrically mounted on the element and projecting from its face into the plunger groove; a hollow handle projecting laterally from the head housing; and means in the handle for rotating said element; that portion of the groove carrying the pin during the movement of the plunger from its withdrawn to its extended position being of a width substantially equal to the diameter of the pin and the remaining portion of the groove being wider for allowing the plunger to rebound independent of the housing during the return of the plunger to its withdrawn position.

References Cited UNITED STATES PATENTS 562,086 6/1896 Livingstone 74--50 1,633,995 6/1927 Miller 173-139 X 2,113,084 4/1938 Hewitt et al 74-55 X 2,240,598 5/1941 Wilke 173117 X 2,298,845 10/1942 Schniied 173-139 X 2,699,745 1/1955 Ayres 74-50 X 2,877,820 3/1959 Ristow 173-418 X CHARLES E. OCONNELL, Primary Examiner.

DAVID H. BROWN, Examiner. 

5. A POWER HAMMER COMPRISING: AN ELONGATED HEAD HOUSING; A PLUNGER JOURNALLED IN THE HOUSING FOR LONGITUDINAL RECIPROCATING MOVEMENT THEREIN AND SPRING-BIASED IN THE DIRECTION FROM A WITHDRAWN TO AN EXTENDED POSITION; A TOOL HEAD MEMBER JOURNALLED COAXIALLY WITH THE PLUNGER FOR LIMITED LONGITUDINAL RECIPROCATING MOVEMENT IN THE HOUSING AND HAVING A PORTION NORMALLY PROJECTING FROM ONE END OF THE HOUSING, SAID MEMBER BEING SPRING BIASED TOWARD A NORMAL POSITION SO AS TO BE STRUCK BY THE PLUNGER WHEN IT MOVES SUBSTANTIALLY HALF WAY FROM ITS WITHDRAWN TO ITS EXTENDED POSITION AND BEING MOVABLE AGAINST THE BIAS OF ITS SPRING WHEN STRUCK BY THE PLUNGER; THE PLUNGER HAVING A TRANSVERSE FLAT SURFACE HAVING A GROOVE THEREACROSS; A ROTATING ELEMENT JOURNALLED IN THE HOUSING AND HAVING A FACE ABUTTING THE PLUNGER FLAT SURFACE; A DRIVE PIN ECCENTRICALLY MOUNTED ON THE ELEMENT AND PROJECTING FROM ITS FACE INTO THE PLUNGER GROOVE; A HOLLOW HANDLE PROJECTING LATERALLY FROM THE HEAD HOUSING; AND MEANS IN THE HANDLE FOR ROTATING SAID ELEMENT; THAT PORTION OF THE GROOVE CARRYING THE PIN DURING THE MOVEMENT OF THE PLUNGER FROM ITS WITHDRAWN TO ITS EXTENDED POSITION BEING OF A WIDTH SUBSTANTIALLY EQUAL TO THE DIAMETER OF THE PIN AND THE REMAINING PORTION OF THE GROOVE BEING WIDER FOR ALLOWING THE PLUNGER TO REBOUND INDEPENDENT OF THE HOUSING DURING THE RETURN OF THE PLUNGER TO ITS WITHDRAWN POSITION. 